Melanoma masquerading as nonmelanocytic lesions.

Abstract

Increased awareness among dermatologists as well as the development of dermoscopy and sequential dermoscopy have contributed significantly toward an increase in the diagnostic accuracy of pigmented melanoma and even of amelanotic melanoma. However, the dermatologist's nightmare is the small group of melanomas that present as common skin diseases, often associated with a significant delay in diagnosis and hence a poor prognosis. The study was carried out to prospectively assess the number of melanomas lacking any clinical suspicion of melanoma and to describe their clinical and histological features over a 6-year observation period in an University Tertiary Skin Cancer Center. Out of 502 cases of newly diagnosed cases of melanoma, seven (1.4%) nonpigmented and nonamelanotic cases of melanoma were identified. The mean age of the patients was 69 years (two females/five males). All cases were discovered by chance on a punch biopsy. The clinical diagnostic suspicions were basal cell carcinoma, fungal intertrigo, keratoacanthoma, lichenoid keratoma, diabetic foot ulcer, eczema, and necrotic pressure ulcer. Dermoscopy, performed after the punch biopsies, was only partially contributive. The mean histological thickness was 2.7 mm, the mean number of mitoses was 7/mm, local micrometastases were present in 5/7 (71%), the mean Ki67 count was 18.9%, and a positive sentinel lymph node was observed in 4/6 (66%) cases. Nonpigmented and nonamelanotic melanomas are rare, are at high risk, and have a poor prognosis because of a delayed diagnosis. Dermoscopy is only of partial diagnostic aid. Treatment resistance or atypical behavior of the above-mentioned lesions should lead to biopsy.